Vineyard research helping crack the pepper puzzle
Groundbreaking vineyard research is helping provide Australian grapegrowers and researchers with a new level of understanding, and potential control, of the development of rotundone in Shiraz.
The Australian Wine Research Institute’s (AWRI) Sensory and Flavour Research Manager Leigh Francissummarised recent research at the Shiraz Symposium held in June in Melbourne, which was funded as part of the AGWA R&D Regional Program for Greater Victoria.
Dr Francis said the presentation was an opportunity to refresh everyone’s memory on current knowledge around rotundone and cool climate Shiraz, as well as introduce the new work being done on viticultural influences.
The paper, Within-vineyard variation in the ‘pepper’ compound rotundone is spatially structured and related to variation in the land underlying the vineyard (Scarlett, N.J., Bramley, R.G.V., Siebert, T.E. 2014), is the latest research to be published in the Australian Journal of Grape and Wine Research. (Contact the AWRI library for a copy http://www.awri.com.au/information_services/publications/ or email@example.com).
The paper looks at the very large variability in rotundone levels across a single Mt Langi Ghiran vineyard, from 73–1082 ng/kg.
“This is almost certainly the first such comprehensive vineyard spatial study on a key grape flavour compound,” Dr Francis said.
“The research shows the variability seems to be related to aspect and soil properties, with ambient temperature and/or solar radiation pointed to as the underlying cause.”
The work was conducted as a collaboration with the late Nathan Scarlett, of the Rathbone Wine Group, and with Dr Rob Bramley of CSIRO.
The Mt Langi Ghiran winery is a long-term collaborator with the AWRI and the onsite vineyard variability research, led by Dr Bramley and Dr Markus Herderich, will continue for another season, with AGWA recently approving continued funding for the project.
“As part of this we are keen to assess the effect of temperature in the vineyard. Work with Pangzhen Zhang, who is conducting a PhD project at the University of Melbourne supervised by Kate Howell, Snow Barlow, Markus Herderich and Mark Krstic, also involves assessing temperature and light effects on variations in rotundone,” Dr Francis said.
“We’re also looking to see if Botrytis, possibly at low levels, might influence the metabolism of rotundone production.
“It would be terrific to assess clonal differences in Shiraz as well. This has been done to some extent but data collected from samples from major clonal collections has been inconclusive, as they are located in warmer climate areas with little or no rotundone detected.”
The Shiraz Symposium also heard about new research, soon to be published, being conducted by Olivier Geffroy and colleagues of IFV Sud-Ouest (Institut Français de la Vigne et du Vin Pôle Sud-Ouest) in France, and AWRI scientists Tracey Siebert and Markus Herderich.
“The research indicates that leaf removal around bunches has a significant effect in lowering rotundone concentration in wines made from the Duras variety in the south of France, and confirms earlier observations with Shiraz that rotundone is produced in the berry late in the season,” Dr Francis said.
Dr Francis said it’s clear that there is a great deal of interest in the topic – particularly among cool climate Shiraz producers.
“It’s well-known that cool-climate, premium Shiraz can show the peppery/spicy flavour and it is a point of difference from warmer climate wines that is well received by buyers of these distinctive wines,” he said.
“I think that with a few somewhat cooler vintages winemakers are becoming increasingly interested in the flavour, and there are more wines with the character on the market in recent years due to slightly milder seasons.
“Now, producers are keen to understand and control the flavour, making sure it is not necessarily dominating but complements other flavours in the wine.”